Advanced Bionics impedances are measured in the monopolar electrode coupling mode, with impedance measurements made on all16 intracochlear electrodes with the case ground electrode serving as the terminal point of the return path. The normal range of electrode impedance values in the Advanced Bionics CII and 90K implants ranges from 1.0 to 30.0 kOhms and in the C1 implants ranges from 1.0 to 150 kOhms. Electrode impedance results are depicted in bar graph form in the electrode impedance tab measurement field. Electrodes with normal impedances are displayed as green bars indicating that they are serving as "valid" functioning electrodes (see Figure 4-8). "Open" electrodes possess impedance values that are higher than the normal range and are displayed in yellow on the bar graph. As mentioned before, when electrode impedances are slightly outside of the normal range (e.g., within 10 kOhm of the upper limit of normal) at implant activation or after a long period of non-use, it is recommended that the clinician provide electrical stimulation to the electrode contacts for a few minutes and then readminister the impedance test. "Short" electrodes are defined either as a single electrode with an impedance value between 0.5 and 1.0 kOhms or as an electrode having a significant electrical interaction with one or more other electrodes. Electrode shorts are displayed in purple in the bar graph display. Finally, electrodes with impedances below 0.5 kOhms are considered to be "invalid" and are displayed in the color gray in the bar graph display. Short electrodes should definitely be disabled and excluded from use in the recipient's program. Open and invalid electrodes should also be disabled if they are persistently outside of the normal impedance range. Advanced Bionics SoundWave software utilizes a form of electrical field imaging and modeling to identify electrode shorts. With the electrical field imaging technique, a small amount of current is sent to an electrode via monopolar electrode coupling, and the resultant voltage that is present at every other electrode in the array relative to the stimulated electrode/monopolar ground connection is measured and compared. Shorted electrodes possess abnormally low electrode impedance values and will show a measured value that is close to that of the stimulating electrode. Within the impedance tab, the clinician also may perform electrode conditioning to eliminate any substances present at the electrode contact (i.e., protein deposits, air bubbles) through the application of a low-level current. These unwanted